Applying for beamtime at the AS MEX1 and MEX2 beamlines

Summary

This document consists of a set of guidelines to prepare quality proposals at the Medium Energy X-ray absorption beamlines, MEX1 and MEX2.  The MEX1 beamline offers similar capability to the XAS beamline, but has reduced flux and a smaller energy range (3.5 – 13.8 keV).  The MEX2 beamline (energy range 2.1 – 3.2 keV) is more similar to the NEXAFS system at the Soft X-ray beamline.  Please ensure that you read this entire document, it is similar (but not the same) as the XAS beamline guidelines, as failure to follow these guidelines is likely to render your proposal uncompetitive.

Beamtime applications will first be assessed against technical feasibility and safety (Yes/No pass criterion). It is thus very important that the technical feasibility of your experiment is 100% clear and you have chosen the correct MEX-1 or MEX-2 beamline.  The primary way to do this in the proposal is via the sample table included as part of the Proposed Experiment section. In the proposal webform, you will find the Proposed Experiment section under the “Beamline” tab.

Applications will further be scored and ranked according to: Quality of the scientific proposal (includes clarity and scientific merit); National benefit and application of the proposed research; Track record relative to opportunity; and Need for synchrotron radiation. For further information on scoring criteria, see also https://archive.synchrotron.org.au/images/20160616--Australian-Synchrotron-access-model.pdf

Fill in the below checklist BEFORE submitting your proposal

If you answer “NO” to any of these questions; STOP.  Go back and take the necessary steps to answer “YES”, otherwise your proposal is likely uncompetitive.

Tips for preparing a proposal

• Beamtime applications will first be assessed against technical feasibility and safety (Yes/No pass criterion). It is thus super important that the technical feasibility of your experiment is 100% clear and you have chosen the correct MEX1 or MEX2 beamline.

• Give yourself plenty of time to develop your proposal. A proposal “hastily thrown together” may save you time, but may not be competitive and thus waste the time of the reviewers and members of the program advisory committee.

• If you need to consult with the beamline scientist team, give them enough time to work with you ahead of the proposal deadline. You are not the only person wanting their input.

• Be clear, concise and to the point. Avoid irrelevant information.

• Make sure you propose an experiment that is feasible (see below for more detail).

• Consider the skills required to make a beamtime successful. Who would be attending the experiment? Will the right people be available? - If you do not (yet) have the skills or knowledge in your team, consider collaborating with someone experienced in your field. Feel free to ask the beamline team for advice.

• Check your proposal PDF before you submit it! Make sure the relevant information is complete and easily found by the reviewers.

Resubmissions

Is your proposal a re-submission of a previously unsuccessful one? If yes, please provide concise information (max 50 words) on how this proposal was improved or changed. Upload this as a short list of dotpoints as a figure with sufficient resolution.

Technical feasibility and your proposed experiment

For the most current information on beamline capabilities, please consult the beamline’s webpage:

MEX Beamline user wiki

Listed below are common reasons why a proposal may be marked technically infeasible and get rejected. This can almost always be avoided by talking to the beamline scientist team first.

• In-situ experiments. MEX is not yet taking in-situ experiments. Those should be submitted to XAS beamline.

• Safety concerns. Explicitly say what the potential risks are that are associated with your experiment or equipment. Examples of problems encountered in the past include: Your experiment uses high pressure, toxic gases, high voltage, etc, and you have not contacted us to discuss safety; your experiment produces toxic gases, but you do not tell us how much; we note that there are electrical hazards, but there is not enough information to be sure; etc. Remember: Risk = Hazard x Exposure.

• Wrong beamline. Past occurrences include proposals for NEXAFS experiments at the Soft X-ray beamline (e.g., C-K edge studies) and XANES imaging measurements at the XFM beamline. Note that MEX1 and MEX2 are two different beamlines.  Make sure you are applying for the correct beamline.

• Insufficient experimental detail. Most often this means there is no table giving detail on samples, detection mode, concentrations, edges, scan times, etc. Thus, we do not know what you are trying to do and how long it should take.
  Other examples include: you mention in-situ setups or measurements but have not talked to the beamline scientists about this; you bring a specialised apparatus, but it is unclear whether or how it will fit into the beamline environment; etc.

• Conflicting or confusing information. The experimental plan is confusing or conflicting with the rest of the proposal. It is thus unclear what the experimental parameters are.

• Closely spaced absorption edges and/or overlapping fluorescence lines from different elements in your sample.  The mix of sample elements means that the corresponding absorption edges are too close together to perform the measurements you need to answer your scientific questions. In the case of fluorescence XAS, there are overlapping fluorescence lines, which means signals from two elements cannot be separated. Watch out for first row transition elements or complex mixtures of lanthanide group elements.

• Highly diffracting materials. Xray Absorption Spectroscopy does not work well on crystalline materials. Especially in case of films on a crystalline substrate, there are issues with fluorescence detection. Talk to the beamline scientist team first.

• Liquid or moist samples at room temperature. The X-ray beam almost always generates bubbles in liquids, thus rendering XAS spectra unusable. In wet or moist samples, radiation damage sets in very quickly. We expect this to be less of an issue on MEX than XAS, however you should talk to the beamline scientist team first.

Writing the Proposed Experiment section

For the experimental section, consider these important points:

• Insert the correct text under the appropriate headings. The experimental section is not an extension of the ‘Scientific Purpose’ or ‘National Benefit’ sections – please only provide information that is relevant to the measurements. Information about the scientific merit or national benefit placed in the experimental section will be ignored. Neither is this the place to describe the synthesis or treatment of your sample material.

• Sample table: A quick reference guide to your experiment. The table needs to show details such as, sample type (sample, reference), absorption edge, concentration, intention (number of scans, duration), state (e.g. solid, powder, liquid), measurement temperature (RT, cyro), environment (for MEX2 - vacuum, Helium) estimated time and detection method (fluorescence/transmission). Be concise, sample grouping is permissible and encouraged. The template provided below shows a non-exhaustive range of possibilities to supply the information required. Once filled in, either cut-and-paste it into the webform or upload it as a screenshot/figure. An example of a simple Proposed Experiment section and corresponding table are given below

• If you have complementary data from other techniques that will aid in assessing the viability of your proposed experiment, describe such results. Include figures as required. Please do not include irrelevant information.

• The first few hours of beamtime are routinely required for beamline conditioning and user training even when the beamline is running smoothly. Estimate a 4 hr overhead for said activities (8 hr if you are a new to the MEX beamline).

• A rough guide to estimating experiment overheads:

Example: Proposed Experiment section

Example of a basic Proposed Experiment section for a MEX-1 proposal. For more complex experiments (e.g., in-operando studies), additional detail needs to be included. Please consult with the beamline scientist team to discuss such details or questions.

Proposed experiment:

“We will measure 64 ex-situ powder pellet samples at the MEX-1 beamline, (i) 13 powder standards of Br and Zn, and (ii) 51 samples in powder form sourced from our experiments conducted at XXX University. These samples will be produced at XXX University using a variety of treatment conditions and tested at the beamline ex-situ.

Sample Preparation: We will prepare powder pellet samples at our home institution or in the synchrotron chemistry lab the days prior to our beam time. The samples will be diluted with cellulose to approximately 1000 ppm of the target element for fluorescence-mode measurements, OR to an edge step in the range of XX for transmission mode. The mixtures will be made homogeneous using a mortar and pestle, compressed into a 7 mm diameter pellet using a hand press and mounted on a MEX-1 PMMA sample holder.

Beamline Setup: Using the Si(111) monochromator in step scan, we will measure the K edges for Br and Zn calibrated with Zn metallic foil, as K edges for Br and Zn fall at 13,473.7 eV and 9,658.6 eV. The sample environment will be room temperature and under helium. Data will be collected to reach K = XXX for EXAFS with duplicate scans.”

Sample Table

Open

Sample Table template BELOW. You may copy and paste this into your proposal and modify to suit your experiment. Concentration is particularly important for the beamline team to determine feasibility. Failure to provide an appropriate concentration increases the chances your experiment will be deemed infeasible. Furthermore, it is vital you know the composition of your sample if you want to make a successful x-ray absorption spectroscopy measurement. The way you present concentration in the sample table depends on the analysis mode (fluorescence, F; transmission, T; or drain current, D) you wish you use:

• Fluorescence (MEX-1 & MEX-2) - express the concentration of the element of interest in one of the following units:

  • weight percent

  • part per million (ppm)

  • millimolal (liquid samples only)

  • samples measured in fluorescence are susceptible to over absorption (also referred to as self-absorption). Good fluorescence samples have 2000 ppm or less of the element of interest. If your samples have weight percent abundance, you will have to dilute them, or develop a strategy for correcting for self-absorption.

• Transmission (MEX-1 only)

  • edge step (Δμd) and total absorption (μd)

  • it is vital you understand the composition of your sample, and the properties that make a good transmission sample. See this comprehensive guide for how to calculate the appropriate dilution for transmission samples in pellet form.

• Drain current (MEX-2 only) - express the concentration of the element of interest in one of the following units:

  • weight percent

  • part per million (ppm)

A common mistake seen in proposals from the catalysis community is to report metal loading in the concentration column. A metal loading is not a concentration. Metal loadings do not help the beamline team assess whether your samples are appropriate for x-ray absorption spectroscopy measurements, but do communicate that you have failed to read this guide. Knowing only the metal loading also rarely helps you, the user, to prepare appropriate samples. If you do not know the exact composition of your sample, you are going to have to develop a strategy to produce samples which give you an opportunity measure good data. That may involve preparing the same material at a range of dilutions to cover the possible range of concentration of the element of interest. If you do not know your composition, and your amount of sample is limited, your experiment is likely to be difficult.

Outcome of previous Australian Synchrotron experiments (past 3 years)

Include tabulated information about publication and outcomes of past beamtime using below template. If there are no outcomes yet, provide information when they can be expected. If previous results are insufficient for producing outcomes, give reasons.

Please note, the list of papers auto-generated by the proposal system is not a substitute for this section.

If you are new to synchrotron radiation experiments, provide evidence of your experience in your field, list your key publications and describe how synchrotron radiation will advance your science. Note that if you are a student you cannot be the Principal Investigator.

The need to use Synchrotron Radiation

Justify why XAS measurements are required for your samples and why the information you seek cannot be obtained using other techniques. Since XAS is not a laboratory-available technique, the need for access to synchrotron radiation to perform XAS measurements is considered a given, so in this section focus on why you need to perform an XAS experiment.

Experimental needs, special requirements and hazards

Be as specific and as concise as possible, particularly if you intend to use your own equipment. User-supplied equipment must comply with the safety requirements of the facility before arrival on site. If you seek to use your own equipment or perform a ‘non-standard’ experiment, you have to consult with the beamline scientist team before submitting your application.

NOTE:  MEX is not currently accepting in-situ experiments.